topic Re: Difference between dates in Statistical Procedures

Difference between dates

ammarhm — Wed, 21 Jan 2015 10:08:15 GMT

I have imported an excel file containing two dates columns, formated as yymmdd

I am trying to find the difference between these two columns

I used the code below but it is returning some strange results

data want;

set have;

format regtime start_date yymmdd10.;

NumDays = intck( 'day', start_date, regtime );

run;

Any help is appreciated

Regards

Re: Difference between dates

mohamed_zaki — Wed, 21 Jan 2015 10:59:39 GMT

post sample from the have dataset

Re: Difference between dates

KachiM — Wed, 21 Jan 2015 11:01:54 GMT

Your CODE is Fine.

Better to see your example.

Re: Difference between dates

Jagadishkatam — Wed, 21 Jan 2015 11:15:04 GMT

I believe the strange result is because of the date format used.

could you please convert the dates to date9. format and then use the intck function.

Thanks,

Jag

Re: Difference between dates

RW9 — Wed, 21 Jan 2015 11:29:00 GMT

You don't actually need that function. If both of your variables are date variables, then they are stored as the number of days since a certain timepoint. Therefore if you subtract one from the other you get the number of days between:

num_days = start_date - regtime;

However, I also concur with the above posters, post example data as the term Regtime indicates that you are looking at a time variable not a date. Or possible a date/time variable. If so then just do:

num_days = start_date - datepart(regtime);

Re: Difference between dates

ammarhm — Wed, 21 Jan 2015 18:37:11 GMT

Here is a sample of the file

The variables are not formated as date in the Excel file but I thought it wouldn't be a problem as I am applying a date format in the SAS code then

As I mentioned, the date formate here is yymmdd

Thanks in advance

Re: Difference between dates

BurntDirt — Wed, 21 Jan 2015 19:01:05 GMT

I think it is the way that you are importing these.

If you just use a simple proc import, it will import these as numeric and not as SAS dates.

SAS dates are also numeric, but they reference the number of days since 1/1/1960.

What you are getting are the numeric values

Obs Start_date regtime

1         120305         140224
2         120319         140224
3         120227         140224

You need to convert these to SAS dates or import them as SAS dates.

To convert them to SAS dates, you can do something like

data want;

set have;

sas_start_date = input(compress(put(start_date,best8.)),yymmdd6.);

sas_regtime = input(compress(put(stat_date,best8.)),yymmdd6.);

NumDays = sas_regtime - sas_start_date;

run;

Re: Difference between dates

RW9 — Wed, 21 Jan 2015 19:28:52 GMT

Yes, as BurntDirt has mentioned those are just numbers, and it is just guessing what they represent, is 120305 = 12Mar05, or 05Mar12 or something else?? Also little tip, don't use proc import as it basically guesses what you want to do. There are many ways to get data in, I would advise that flat text file delimited, e.g. CSV, is best. Then write a datastep import program specifically tailored to the data you know best.

Re: Difference between dates

Patrick — Wed, 21 Jan 2015 20:29:03 GMT

The date format applied has no influence on the result returned by the intck() function as the function uses the internal numeric value.